Regeneration system for a transmitted telegraph signal



KOJI TADENUMA A ril 1, 1969 REGENERATION SYSTEM FOR A TRANSMITTEDTELEGRAPH SIGNAL Sheet Filed Jan. 21, 1966 FIG.

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KOJI TADENUMA April 1, 1969 REGENERATION SYSTEM FOR A TRANSMITTEDTELEGRAPH SIGNAL Filed Jan. 21. 1966 Sheet FIG.

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United States Patent 3,436,481 REGENERATION SYSTEM FOR A TRANSMITTEDTELEGRAPH SIGNAL Koji Tadenuma, Tokyo-t0, Japan, assignor to KokusaiDenshin Denwa Kabushiki Kaisha, Tokyo-to, Japan, a joint-stock companyof Japan Filed Jan. 21, 1966, Sei'. No. 522,235 Claims priority,application Japan, Jan. 25, 1965, 40/ 3,652 Int. Cl. H04l 25/20, 25/52US. Cl. 178-70 3 Claims This invention relates to a regenerating systemfor a transmitted telegraph signal.

In the conventional transmission system for a telegraph signal, it isnecessary that a pass band of more than W cycle/second be assured tocorrectly detect a transmitted telegraph signal having the highesttelegraph modulation frequency (W/2) cycle/second. As known in the art,a wave frequency-modulated by a rectangular wave can be represented bythe following equation:

2m 1 e= sm (ma/2) cos wt where w=angular velocity of the carrier wavem=modulati0n index (Af/Zp) Af=shift frequency p=angular velocity of therectangular wave In proportion to the increase of the modulationfrequency (p/21r), the respective frequency spacing between adjacentspectrums of side bands components the angular velocity of which arerepresented by values (wp), (w-l-Zp), (cu-2p), (w-i-Zp) increases. Ifthe modulation frequency (p/21r=W cycle/second) is over one half thebandwidth of the transmission channel, a spectrum of the side bandcomponents cannot be transmitted. In such a condition, the carrierfrequency only is included in the transmitted wave, so that therectangular wave transmitted cannot be regenerated in the conventionalregenerating system. A telegraph signal, such as that of a S-unit codeor 7-unit code, generally includes spectrums of modulation frequencywhich are multiples of the frequency of the code element. Accordingly,code elements the polarity of which are alternatively changed are atfirst destroyed in accordance with decrease of their pass bandwidthsince the frequency of a code element is the highest modulationfrequency.

An object of this invention is to provide a regenerating system for atelegraph signal transmitted through a telegraph pass-band narrower thantwice the highest telegraph modulation frequency of the signal.

According to the present invention there is provided a regeneratingsystem for a transmitted telegraph signal, comprising a rectangular waveoscillator having a frequency substantially equal to the frequency ofthe code element of the transmitted telegraph signal, a level detectorfor detecting whether or not the instantaneous level of the transmittedtelegraph signal exceeds a predetermined level range and for detectingthe polarity of the excess level of the transmitted telegraph signalfrom the level range, control means for causing, only when the leveldetector detects that the instantaneous level does not exceed the levelrange, the oscillator to generate a rectangular wave having thefrequency of the code element of the transmitted telegraph signal andfor causing,

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when the level detector detects that the instantaneous level exceeds thelevel range, the oscillator to change the polarity of the rectangularwave in accordance with the polarity of said excess level, whereby aregenerated telegraph signal is derived from the oscillator.

The novel features of this invention are set forth with particularity inthe appended claims. This invention, however, as to its construction andoperation together with advantages thereof, may best be understood byreference to the following description, taken in connection with theaccompanying drawings in which the same or equivalent parts aredesignated by the same or similar reference numerals or characters, andin which:

FIG. 1 is a block diagram of an embodiment of this invention;

FIG. 2 is a connection diagram for illustrating a rectangular waveoscillator and control means of this invention; and

FIG. 3 shows waveforms for describing the operation of the circuitillustrated in FIG. 1.

Referring to FIGS. 1 and 3, the principle of this invention will firstbe described. The embodiment of this invention shown in FIG. 1 comprisesa rectangular wave oscillator 4, a level detector (3a and 3b), andcontrol means (5a and 5b). It is assumed that a telegraph signal V (FIG.3) of W bands is transmitted through a telegraph pass band narrower than(W/2) cycle/second and that the signal is received and applied as a waveV to an input terminal 1. Code elements E E E and E of the wave V aremodulated with a frequency W/2 cycle/second, and the modulated signalcannot be transmitted through the pass-band (W/Z) cycle/second, so thatinstantaneous levels of the transmitted wave V corresponding to thesecode elements are Zero as shown. The transmitted wave V is applied tothe level detector which is composed of, for example, a pair of triggercircuits 3a and 3b. These circuits 3a and 3b respectively have triggerlevels Va and Vb and detect whether or not the instantaneous level (e ofthe transmitted telegraph signal V exceeds a predetermined level rangeVaVb. The transmitted wave V is converted, by the trigger circuits 3aand 3b, to rectangular waves V and V which are applied to therectangular Wave oscillator 4 through terminals 5a and 5b. The polarityof waves V and V indicates the polarity of the excess level of the waveV from the range Va-Vb; that is, durations (r 4 (r 4 and (t -r are plus,and durations (tot1), (tg-tn), and (Hz-tn) are minUS..The frequency ofthe oscillator 4 is substantially equal to the frequency of the codeelement of the transmitted telegraph signal V and is controlled by theoutputs 5a and 5b of the level detector (3a and 3b). The oscillator 4operates under the following conditions:

(i) Only when the level detector (3a and 3b) detects that theinstantaneous level (e,) of the wave V does not exceed the level range(Va-Vb) by more than the duration T of the code element (E E E theoscillator 4 generates a rectangular wave V having the frequency (W/ 2)of the code element of the transmitted telegraph signal V (ii) When thelevel detector (3a and 5b) detects that the instantaneous level (eexceeds the level range (Va- Vb): the oscillator change the polarity ofa rectangular wave (V in accordance with the polarity of the excesslevel.

By combination of these operations (i) and (ii), a regenerated wave Vcorresponding to the transmitted telegraph signal V is derived from anoutput terminal 2 of the oscillator 4.

An example of the rectangular wave oscillator 4 is illustrated in FIG.2. In this embodiment, transistors Tr and Tr form an astablemultivibrator 4a, together with time constant circuits each composed ofa resistor (R or R and a capacitor (C or C and a bias circuit composedof a resistor R and a capacitor C Terminal 2a (or 2b) is the outputterminal of this multivibrator 4a for deriving therefrom the rectangularwave V The collectors of transistors Tr and Ta; are respectivelyconnected to the bases (control electrodes) of the transistors Tr and Trand the emitters of the transistors Tr and Tr, are connected to theearth (ground) potential. The resistances of the collector-to-emitterpaths (PH;, and PH of the transistors Tr and Tr are adjusted to low orhigh values by applying the waves V and V respectively, to terminals 5aand 5b (which are respectively connected to the bases of transistors Trand Tr.;). Accordingly, the base-to-emitter paths (PH; and PH of thetransistors Tr and Tr are adjusted so as to be open or shorted(particularly, through the bias circuit of R and C by the waves V and Vapplied to the terminals 5a and 5b.

Only when both of the paths (PH, and PH are in the open state, theoscillator 4a operates, as an astable multivibrator changing thepolarity of its output, at a frequency determined by the value of thetime constant circuits (R C and R C When either of the short states ofthe paths (PH and PH is established, the oscillation of the oscillator4a stops, and the polarity of the output of the oscillator 4a is changedto the plus or minus state in accordance with the alternative shortstate of the path (PH or PH Referring to FIG. 3, operation of theoscillator 4a will now be described in detail.

(1) Time interval (t t ).-The polarity of the wave V only is plus, andthis plus potential is applied to the terminal b. Since the base of thetransistor Tr, becomes plus, the path PH of the transistor Tr isestablished to pass through low resistance through which the base of thetransistor Tr is connected to earth potential. Accordingly, thetransistor Tr is cut off by the bias voltage across the bias circuit (RC and, therefore, a current (i,) from a source (+E) flows through onlythe transistor Tr As a result of the potential difference across aresistance R the polarity of the output (V becomes minus.

(2) Time interval (t t ).The polarity of the wave V becomes minus at thetime 1 Because this minus voltage cuts off the transistor Tr the basepotential of the transistor Tr rises abruptly. In this case, since thecollector potential of the transistor Tr is high while the collectorpotential of the transistor Tr is low, the current from the source (+E)surges into the transistor Tr Accordingly, the transistor Tr becomes ON,and the transistor Tr is cut off (OFF state).

As a result of these operations, the collector potential of thetransistor Tr, rises abruptly. Moreover, since these operations arecarried out in an instant, the abrupt rise of the collector potential ofthe transistor Tr occurs simultaneously with the transition instant (1(plus to minus) of the wave V In this time interval (t t the polarity ofthe output (V is plus, which is sustained to the time 1 because theduration (1 to t is shorter than the time constant 1- of the timeconstant circuits (R C R C (3) Time interval (t -t ).--The polarity ofonly the wave V becomes plus at the time 1 This plus potential isapplied to the terminal 5a and makes the resistance of path PH low. Thislow resistance causes the transistor Tr to be cut off. However, theoutput potential V is not changed since the transistor Tr has been cutoff at the time t1.

(4) Time t .The polarity of the wave V becomes minus at the time tBecause this minus voltage cuts off the transistor Tr the base potentialof the transistor Tr rises abruptly. In this case, since the collectorpotential f he tran i r To is high while the collector potential of thetransistor Tr is low, the current from the source (+E) surges into thetransistor Tr Accordingly, the transistor Tr becomes ON, and thetransistor Tr is cut oif (OFF state). As a result of these operations,the collector potential of the transistor Tr drops in an instantsimultaneously with the termination instant (t of the plus potential ofthe wave V (5) Time interval (t t ).In this interval, both of theoutputs (V and V are minus. These minus potentials cause the resistancesof the paths PH and PH, to be high, so that the oscillator 4a operatesas an astable multivibrator and generates a rectangular wave V theperiod of which is proportional to the sum of time constants 0;, R and CR (6) Time interval (t t ).-At the time t the polarity of the wave Vchanges to plus, so that the path PH assumes low resistance.Accordingly, the transistor Tr, is cut off, and the transistor Tr;becomes ON. As a result of this operation, the output (V assumes pluspolarity which is sustained from the time t to a time i In this period(t -t the oscillation of the oscillator 4a stops. At the time t the ONstate is switched from the transistor Tr to the transistor Tr; asdescribed with respect to the time t (7) Time interval (t t ).Theoperation during this period is the same as that of the period (t t (8)Time t .-The polarity of only the wave V; becomes plus at the time t,,.This plus potential is applied to the terminal 5b and makes theresistance of path PH low. This low resistance causes the transistor Trto be cut oif. However, the output V is not changed since the transistorTr has been cut off at the time i This state continues from the time Ito the time t Time t11.

At time t since the polarity of the wave V becomes minus, the transistorTr assumes the OFF state, and the path PH, assumes high resistance. As aresult of this operation, the base potential of the transistor Tr risesabruptly, whereby a current i surges into the transistor Tr Accordingly,the ON state is transferred from the transistor Tr to the transistor TrThis state continues until a time i (i) when the duration I to is equalto or less than the duration T: simultaneously with the transition ofthe wave V from minus to plus, the ON state is switched from thetransistor Tr to the transistor Tr (ii) When the duration from the timer to transition instant r is greater than the duration T: in theduration t to r the oscillator 4a operates as an astable multivibrator.Accordingly, the ON state switches, at a time corresponding to thetransition instant of the oscillator 4a, from the transistor Tr to thetransistor Tr At a time r the polarity of the output (V of theoscillator 4a does not change.

(11) Time interval (t -t ).The operation in this period is the same asthat in the period (t -t (12) Time interval (t -t ).The operation inthis period is the same as that in the period (13-1 (13) Time t .--Theoperation in this period is the same as that in the period (t -tAccording to the system of this invention, since a transmitted telegraphsignal, which has not been regeneratable in the conventional art, due todistortion or destruction of its waveform, can be completelyregenerated, it is possible to transmit, through a limited telegraphpass band, a telegraph signal modulated with a frequency which is morethan twice the modulation frequency in a conventional system. In otherwords, a telegraph signal transmitted through a telegraph pass band ofless than half of the essential width for a conventional system can 'becompletely regenerated by the regenerating system of this invention. Theresulting economical transmission of telegraph signals is an importantfeature of this invention.

The level range can be established in any zone, for example plus voltagezone or minus voltage zone, if suitable.

A telegraph signal transmitted through any transmission system as wellas transmission by frequency modulation, for example transmission byamplitude modulation or D-C transmission, can be completely regeneratedby the regeneration system of this invention.

What I claim is:

1. A regenerating system for a transmitted telegraph signal, comprisingan oscillator for generating a rectangular wave having a frequencysubstantially equal to the frequency of the code element of thetransmitted telegraph signal; a level detector for detecting Whether ornot the instantaneous level of the transmitted telegraph signal exceedsa predetermined level range and for detecting the polarity of the excesslevel of the transmitted telegraph signal from the level range; controlmeans for causing, only when the level detector detects that theinstantaneous level does not exceed the level range, the oscillator togenerate the rectangular wave having the frequency of 20 the codeelement of the transmitted telegraph signal and for causing, when thelevel detector detects that the instantaneous level exceeds the levelrange, the oscillator to change the polarity of the rectangular wave inaccordance with the polarity of said excess level, whereby a re- 25generated telegraph signal is derived from the oscillator.

2. A system according to claim 1, in which the oscillator is composed ofan astable multivibrator, and the control means is composed of a pair ofcontrollable impedances which are respectively connected to controlelectrodes of active elements of the astable multivibrator, said pair ofcontrollable impedances being controlled by the level detector.

3. A system according to claim 2, in which the astable multivibrator iscomposed of a pair of transistors and said control means is composed ofa pair of transistors the collector-to-emitter paths of whichrespectively form said controllable impedances controlled by their basepotentials.

References Cited UNITED STATES PATENTS 2,858,431 10/ 1958 Le Fevre.3,071,733 1/1963 Holzer et al. 3,304,508 2/ 1967 Danielsen et a1.3,390,283 6/ 1968 Hannigsberg.

THOMAS A. ROBINSON, Primary Examiner.

US. Cl. X.R.

1. A REGENERATING SYSTEM FOR A TRANSMITTED TELEGRAPH SIGNAL, COMPRISINGAN OSCILLATOR FOR GENERATING A RECTANGULAR WAVE HAVING A FREQUENCYSUBSTANTIALLY EQUAL TO THE FREQUENCY OF THE CODE ELEMENT OF THETRANSMITTED TELEGRAPH SIGNAL; A LEVEL DETECTOR FOR DETECTING WHETHER ORNOT THE INSTANTANEOUS LEVEL OF THE TRANSMITTED TELEGRAPH SIGNAL EXCEEDSA PREDETERMINED LEVEL RANGE AND FOR DETECTING THE POLARITY OF THE EXCESSLEVEL OF THE TRANSMITTED TELEGRAPH SIGNAL FROM THE LEVEL RANGE; CONTROLMEANS FOR CAUSING, ONLY WHEN THE LEVEL DETECTOR DETECTS THAT THEINSTANTANEOUS LEVEL DOES NOT EXCEED THE LEVEL RANGE, THE OSCILLATOR TOGENERATE THE RECTANGULAR WAVE HAVING THE FREQUENCY OF THE CODE ELEMENTOF THE TRANSMITTED TELEGRAPH SIGNAL AND FOR CAUSING, WHEN THE LEVELDETECTOR DETECTS THAT THE INSTANTANEOUS LEVEL EXCEEDS THE LEVEL RANGE,THE OSCILLATOR TO CHANGE THE POLARITY OF THE RECTANGULAR WAVE INACCORDANCE WITH THE POLARITY OF SAID EXCESS LEVEL, WHEREBY A REGENERATEDTELEGRAPH SIGNAL IS DERIVED FROM THE OSCILLATOR.